This is the official page from the Japanese Ministry of Foreign Affairs, which is the department that deals with visas. It states that all foreigners should expect to be photographed, fingerprinted and questioned each and every time they enter Japan. They do not mention anything having to do with felony convictions. Therefore, you are going to have to contact the Japanese embassy and ask them what their policy is. This is the web page  that has the list of the various embassies.